I use a 50" Panasonic Plasma for my PC. I play games all the time, and haven't really felt any negative effects on my gaming from input lag. Sure there is some on faster paced games, but I only notice it if I'm trying to.
And this is on a "Custom" setting, not even on "Game Mode". With Game Mode I find I don't see any lag at all.
Those TV's you mentioned are a few years old. I would think you could get something a little better and more recent. If I'm not mistaken, Best Buy lets you return things within 30 days of purchasing. So just find a TV you like, try it out with gaming, and return it for another TV if the lag is too much.